A global analysis has found that urban animals are bolder and more aggressive, exploratory and active than their rural counterparts. The findings are published in the British Ecological Society's Journal of Animal Ecology.
Researchers at Lewis & Clark College (Portland), CEFE-CNRS in Montpellier, and North Dakota State University have conducted a first of its kind, global meta-analysis of how animal behaviour varies between urban and non-urban populations of birds, mammals, amphibians, reptiles and insects.
They found that urban populations exhibited heightened boldness, aggression, exploration, and activity compared to rural counterparts. These findings were most pronounced in birds, but the researchers caution that there was much more limited data on the other animal groups.
Dr Tracy Burkhard, Assistant professor of biology at Lewis & Clark College, and first-author of the study, said: "We found that no matter where you are in the world, urbanisation is changing behaviour in consistent predictable ways. The strongest result was that animals seem to be more risk positive. They're more bold."
The researchers warn that a shift towards these traits could increase the risk of human-wildlife conflict and zoonotic disease transmission.
"If animals are more risk-taking and they're less averse to human presence, we're going to be coming into contact with wildlife a lot more in certain areas, and that is potentially bad for both us and wildlife." said Dr Burkhard.
The researchers also warn that it's not just species that we're used to seeing in cities - like rats, gulls and pigeons - that are becoming bolder. The same behavioural shifts are being seen in species that are more commonly associated with rural habitats, but which are now adapting to urban life, such as whitethroat, yellow hammer and redpoll.
The results highlight the need for urban planners to consider animal behaviour, especially as urbanisation increases. This could include creating connected greenspaces to maintain connectivity and gene flow among urban animal subpopulations.
In the analyses, the researchers combined data from 80 existing studies that looked at animal behavioural traits. These studies spanned 28 countries and 133 distinct species. Over 70% of the research was on birds, with insects, amphibians and reptiles making up just 10% of the data, indicating that most species remain understudied in terms of the effect of urbanisation on behaviour.
Dr Anne Charmantier, Research Director (DRCE) at CNRS, University of Montpellier, and a co-author of the research said: "Our study shows that the research effort is very imbalanced across taxa; in particular birds are much more commonly studied than amphibians, reptiles or insects. The lack of data in some animal classes limits some of our conclusion and should be seen as an encouragement to study all organisms living in cities."
